When using a wire electrical discharge machine to successively machine workpieces, having the operator predict the time of end of machining on one workpiece so as quickly start to prepare for the machining of the next workpiece after the end of that machining is important for raising the operating rate of a facility.
Conventionally, the time of the end of machining in wire electrical discharge machining is predicted by using a reference machining speed provided by the machine manufacturer or by using a machining speed calculated by the user based on past actual data (hereinafter both called the “predicted machining speed”). Alternatively, to further raise the precision of estimation, as shown in PLT 1, sometimes the actual machining speed detected during machining is used for prediction of the time of end of machining in place of the predicted machining speed. In this case, the remaining machining time is displayed while being updated every instant.